A survey of leaf-litter spiders was carried out in April 2008 and March 2009 at three National Parks in Northern Vietnam, such as, Cuc Phuong National Park (CPNP, red river delta tropical monsoon climate), Tam Dao National Park (TDNP, high mountain tropical monsoon climate) and Cat Ba National Park (CBNP, maritime climate). Four types of habitat chosen at each region are natural forest and disturbed forest (have multi-layer vegetation structure), shrub-land and acacia plantation (have simple-layer vegetation structure). The spiders were sampled by leaf-litter sieving. A total of 8787 adults (251 species, 33 families) from three regions were found, including 2846 adults (142 species) in CPNP, 3184 (137) in TDNP and 2757 (124) in CBNP. Sheet-line weavers and cursorial hunters were the dominant guilds at study area. The MDS plots and ANOSIM analyses used to compare the diversity of leaf-litter spiders between regions and between habitats. The species composition of three regions was significantly different between region with maritime climate conditon (CBNP) and the rest regions. The abundance, species richness and diversity index were higher in habitats that multi-layer vegetation structure. The species and guild composition were considerably different between two types of habitat. The relationships between diversity of leaf-litter spiders and habitat structure as well as the different in species composition between regions have been discussed in the paper.
TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 LEAF-LITTER SPIDER DIVERSITY IN THE TROPICAL FOREST OF NORTHERN VIETNAM IN RELATION TO REGIONAL CONDITION AND HABITAT STRUCTURE Pham Dinh Sac1*, Tran Thi Anh Thu2, Li Shuqiang3 (1*) Institute of Ecology and Biological Resources, VAST, phamdinhsac@gmail.com (2) Can Tho University, Vietnam (3) Institute of Zoology, Chinese Academy of Sciences, Beijing, China ABSTRACT: A survey of leaf-litter spiders was carried out in April 2008 and March 2009 at three National Parks in Northern Vietnam, such as, Cuc Phuong National Park (CPNP, red river delta tropical monsoon climate), Tam Dao National Park (TDNP, high mountain tropical monsoon climate) and Cat Ba National Park (CBNP, maritime climate) Four types of habitat chosen at each region are natural forest and disturbed forest (have multi-layer vegetation structure), shrub-land and acacia plantation (have simple-layer vegetation structure) The spiders were sampled by leaf-litter sieving A total of 8787 adults (251 species, 33 families) from three regions were found, including 2846 adults (142 species) in CPNP, 3184 (137) in TDNP and 2757 (124) in CBNP Sheet-line weavers and cursorial hunters were the dominant guilds at study area The MDS plots and ANOSIM analyses used to compare the diversity of leaf-litter spiders between regions and between habitats The species composition of three regions was significantly different between region with maritime climate conditon (CBNP) and the rest regions The abundance, species richness and diversity index were higher in habitats that multi-layer vegetation structure The species and guild composition were considerably different between two types of habitat The relationships between diversity of leaf-litter spiders and habitat structure as well as the different in species composition between regions have been discussed in the paper Key words: diversity, leaf-litter spider, regional condition, tropical forest, vegetation structure, Northern Vietnam INTRODUCTION Leaf-litter spiders are those inhabiting the forest-floor litter layer Communities of leaflitter spiders frequently exhibit both high family diversity and numerical abundance [43] The studies of Wise (1993), Wagner and Wise (1996, 1997) [43, 39] suggested that the structural complexity of the leaf litter itself may facilitate the persistence of this high diversity of predators Because litter spiders are linked to and reflect habitat structure and prey abundance, they also can act as indicators [20] Leaf-litter spiders had been used as indicators to monitor redwood forest restoration [42] and evaluate the effects of wildfire [21] While prey abundance accounted for a statistically significant amount of variation in leaf-litter spider diversity during the early summer months, litter depth, complexity and temperature were more important during middle and late season [31-33] One possible explanation may be that as the structural complexity of the litter increased, the surface area and diversity of potential foraging spaces within the leaves also increased In particular, the spaces within curled leaves, the underside of twisted leaves or the gaps between leaves create unique foraging sites for a diversity of spiders [29, 34] Like other litter arthropod communities, litter spider community can vary along elevation gradient [22, 36], habitat complexity [8, 41, 36, 1] Their abundance can relative to availability of nutrients [33, 23], litter depth and complexity [33, 5, 6, 38, 40] and fluctuation in environment conditions [12] Herein we present an assessment of diversity patterns for a leaf-litter spider community in the tropical forests in Northern Vietnam Our first goal was to compare the community structure and species composition of spiders between three regions are different in climate condition Our second goal was to relate vegetation structural variables of each type of habitat with that of spider fauna and quantify 59 Pham Dinh Sac, Tran Thi Anh Thu, Li Shuqiang the faunal similarity among different habitat types MATERIALS AND METHODS Study area The study was carried out at three regions (CPNP, TDNP and CBNP) in Northern Vietnam, separated by 140-160 km (fig 1) Phong province Due to the isolated nature of the island, the diversity and abundance of mammals at CBNP are low compared to other national parks in Vietnam The park is located between 20o44’-20o51’N and 106o58’-107o10’E and it covers an area of 15,200 ha, at elevation from 25-331 m The CBNP affected by maritime climate with weather fluctuation In addition, typhoons and tropical storms are frequent in the rainy season Sampling sites Spiders were sampled at four types of habitats in each region Natural forests and disturbed forests belong to types of multi-LVS (four or five vegetation layers) Shrub-land and acacia plantation belong to types of simple-LVS (one vegetation layer) Natural forests (NATF) A five layers structures (A1-A5) follow Thai Van Trung (2000) [30] The highest layer (A1) or emergent canopy consists of woody trees with height of over 30 m with scattered distribution Figure Map of Northern Vietnam and the location study regions Cuc Phuong National Park (CPNP) is situated from 20o14’-20o24’N and 105o29’105o44’E and occupied about 22,200 The park belongs to Ninh Binh province, at elevation 154-636 m above sea level It is located in the red river delta tropical monsoon climate area with stability in factors of weather, such as, temperatures, humidity gradient Tam Dao National Park (TDNP) (21o21’o 21 42’N, 105o23’-105o44’E) belongs to Vinh Phuc province, total area of the park is 36,833 and varies in elevation from 900-1388 m Locating in the area with typical characters of high mountain tropical monsoon climate, TDNP has high humidity, while temperature is very low It is misting and rain together strong win are regular occurrence in this region [10] Cat Ba National Park (CBNP) differs from other national parks in Vietnam by locating in island areas that lies 20 km due east of Hai 60 The layer A2 is composed of woody trees of 20-30m high and makes out a big ecological dominant canopy Layer A3 is a canopy with plants of 8-20 m high and discontinuously distributed with some frequently-observed species Layer A4 consists of plants below m high Layer A5 (forest floor) consists of weedy and shrubby plants Disturbed forests (DISF) In the disturbed forest adjacent to the natural forest, the vegetation has four indistinct tree layers A2, A3, A4 and A5 The highest layer (Al) was absent in disturbed forest because of the logging caused by local people in the past Shrub-lands (SHRL) The shrub-land are not natural but are derived from forest loss The vegetation comprise only shrubs layer with 2-8 m high Acacia plantation (ACAP) Two species of acacia planted commonly TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 are Acacia auriculiformis and Acacia mangium These species have been planted in Vietnam for many years It covers an area of 926 in CPNP, 1530 in TDNP and 784 in CBNP [10, 37] Acacia plantation has one tree layer of Acacia, with an average canopy height of 15-25 m Sampling methods Some methods used in sampling litter spiders are sieving, pitfall trap and Berlese funnel However, litter sieving mainly sample more genera, species and individuals than other methods and contained a greater proportion of small species and specieal species [27] This sifter consists of a heavy cloth cone about 80 cm in length, 30 cm in diameter at one end and 10 cm at the other An open metal frame with a handle attached is sewn into the large end and another similar frame, to which a metal 13 mm mesh size grid is soldered, attached about 25 cm below the first one The narrow end of the cone is tied shut with a rope, so that a bag is formed Leaf-litter placed in the top of the bag rest on the grid, and we shake the sifter, fine debris, including spider falls through the grid and accumulate at the bottom Then, using a peace of plastic for spread out the debris and collecting spiders At each region, four habitats were chose, each habitat consisting of five replications The replications were established at least 50 m from the edge of the forest edge to reduce the edge effect and with a distance about 1.0 km from each of the five replications Spiders sampled in four 0.25-m2 litter samples per replication (1-m2 litter samples in total per replication) Samplings were conducted every month between April 2008 and March 2009 All adult spiders were identified to family and morpho-species Juveniles were excluded from this study due to the extreme difficulties of identification to species level, however, a quantitative assessment of their identities at the family level suggested a similar frequency distribution as with adults [28] Statistical analyses Indices of the Margalef species richness (d), Pielou evenness (J’), Shannon - Weaver function (H’) and Simpson index (D) of spider communities were assessed for each habitat type, and were calculated using Primer v5 software [24] The Shannon-Weaver function and Simpson index used to compare the community structures of spiders among different regions and habitats Samples having high species richness and equal abundance between species will generate higher H values Samples represented by few dominant species and many rare species will generate large D values, therefore, the Simpson index can be used to assess the degree of dominance of the sample The Shannon - Weaver function (H’) and Simpson index (D) are calculated by the following formulas: H’ = -∑Pi LogPi; D = 1-∑ (Pi)2 Where Pi is the percentage of species i in the total community The value of evenness ranges from to 1, which measures the degree of homogeneity in abundance between species The species richness (d) and evenness (J’) are calculated by the following formulas: d = (S-1)∕Log(N); J’ = H’∕Log(S) Where S is total species, N is total individual The t-test of paired two samples for means was used to test the difference of diversity index (Shannon - Weaver function H’) between habitat types by the following formula [28]: H’1 - H’2 t= [var (H1’) + var (H2’)]1/2 The similarity among sampling sites was depicted as Bray - Curtis similarities, using both species and guild compositions Multidimensional scaling plots (MDS) were constructed based upon similarity values Analysis of similarities (ANOSIM) was performed between each pair of habitats and between regions to determine the signification level The ANOSIM procedure of PRIMER is a nonparametric permutation procedure applied to rank similarity matrices underlying sample ordinations [9] This method generates a global R-statistic, which is a measure of the distance between groups An R-value that approaches one indicates strongly distinct assemblages, 61 Pham Dinh Sac, Tran Thi Anh Thu, Li Shuqiang whereas an R-value close to zero indicates that the assemblages are barely separable [9] These R-values were used to compare spider assemblages between regions and between habitats Where ANOSIM revealed significant differences between guilds, SIMPER analyses (PRIMER) were used to identify those guilds that contributed most to the observed assemblage differences [10] Similarity percentages (SIMPER) allowed identification of species and guilds important in discriminating between groups that differed significantly from each other Species accumulation curves were employed to compare the completeness of our sampling for each region It was compared theoretical or expected species accumulation curve, which describes the when data are randomly distributed among the samples SPSS 15.0 computer program (SPSS Inc USA) was used to perform this test Guild composition Based on hunting methods and web building types from the literatures of Uetz (1999) [35], Hofer and Brescovits (2001) [14] we grouped the families of leaf-litter spider collected in Northern Vietnam into the following four guilds: 1) orb weavers: Anapidae, Araneidae, Mysmenidae, Tetragnathidae, Theridiosomatidae; 2) sheet-line weavers: Amaurobiidae, Haniidae, Leptonetidae, Linyphiidae, Ochyroceratidae, Pholcidae, Sicariidae, Scytodidae, Telemidae and Theridiidae; 3) cursorial hunters: Clubionidae, Corinnidae, Gnaphosidae, Liocranidae, Lycosidae, Oxyopidae, Pisauridae, Salticidae, Segestriidae and Zodariidae; 4) ambush predators: Atypidae, Ctenidae, Ctenizidae, Dipluridae, Nemesiidae, Oonopidae, Sparassidae and Thomisidae Among them, web building spiders include web weaver and sheet line weaver guilds, the rest guilds belong to non web building spiders RESULTS Community structure of leaf-litter spiders in Northern Vietnam The species accumulation curves for each region relatively reach an asymptote (fig 2), the sampling was almost complete at three regions, suggesting that our comparisons of species richness between three regions are valid 150 Number of Species 120 90 60 Cuc Phuong National Park 30 Tam Dao National Park Cat Ba National Park 0 700 1400 2100 2800 3500 Number of Individuals Figure Rarefaction curves of leaf-litter spiders in three regions Of the total 24,621 specimens collected at three regions Northern Vietnam, there were 8,787 adults From adult specimens, 251 species of 33 families were identified The three most 62 abundant families were Linyphiidae (19.12% of all captures), Salticidae (13.37%) and Theridiidae (13.35%), followed by Lycosidae (9.96%), Oonopidae (7.89%), Zodariidae TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 (6.05%), Corinidae (5.44%), Amaurobidae (5.35%), the rest families less than 5% for one Ochyroceratidae, Segestriidae; for TDNP: Leptonetidae, Sicaridae, Nemesiidae; for CBNP: Dipluridae, Anapidae Relative abundance (%) The material collected from CPNP consisted of 2,846 adults, 142 species, and 27 families; from TDNP consisted of 3184 adults, 137 species, and 26 families; and from CBNP consisted of 2757 adults, 124 species and 25 families Twenty families of leaf-litter spiders were collected from all of three regions The unique families found for CPNP are: Atypidae, Sheet-line weavers (42.43 % of total capture) and cursorial hunters (41.16% of total capture) were the dominant guilds with the highest number of individuals, followed by ambush predators (12.18% of total capture), lowest was orb weavers (4.23% of total capture) (fig 3) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Ambush predator Cursorial hunter Sheet-line weaver Orb weaver CPNP TDNP CBNP Total Region Figure Variation in guild structure of leaf-litter spider assemblages across different Table Diversity of leaf-litter spider sampled in habitat types of three regions Regions CPNP TDNP CBNP Habitat types Species number (S) Individual number (N) NATF DISF SHRL ACAP NATF DISF SHRL ACAP NATF DISF SHRL ACAP 95 90 75 61 90 94 68 61 84 94 74 66 952 742 607 545 932 1074 572 606 818 784 596 559 Number of species, individuals, species richness, evenness, and indices of diversity of leaf-litter spider communities in three typical regions belong to Northern Vietnam are presented in table Evenness and Simpson Species richness index (d) 13.71 13.47 11.55 9.52 13.02 13.33 10.55 9.36 12.38 13.95 11.42 10.27 Evenness index (J’) 0.8852 0.8954 0.8945 0.8312 0.8332 0.8416 0.9012 0.8993 0.8987 0.8874 0.8892 0.9228 ShannonWeaver function (H’) 4.031 4.029 3.562 3.417 3.749 3.824 3.502 3.497 3.982 4.032 3.627 3.666 Simpson index (D) 0.8749 0.8742 0.8712 0.8283 0.8588 0.8641 0.8685 0.8664 0.8744 0.8725 0.8688 0.8736 index were not significantly different among the four types of habitats, while the abundance, species richness index and Shannon-Weaver function were significantly higher in habitats of multi-LVS than habitats of simple-LVS in all 63 Pham Dinh Sac, Tran Thi Anh Thu, Li Shuqiang three regions The results of t-test also showed the significant difference of Shannon-Weaver function between habitats of multi-LVS and habitats of simple-LVS (P < 0.01) while analysis showed that between habitats of multiLVS and between habitats of simple-LVS were not significantly different (P > 0.05) (table 2) Table Pair-wise t-test the differences of Shannon-Weaver function (H’) between habitats (paired two sample for means, d.F = 250) Comparison NATF vs DISF NATF vs SHRL NATF vs ACAP DISF vs SHRL DISF vs ACAP SHRL vs ACAP t-test 1.78 2.71 2.39 2.24 2.52 0.45 CPNP P(T ≤ t) 0.3789 0.0036 0.0086 0.0074 0.0069 0.3269 Comparison of species and guild composition among three regions The MDS plots generated from relative abundances of different spider species in t-test - 0.91 2.46 2.18 3.15 2.89 - 0.67 TDNP P(T ≤ t) 0.1809 0.0087 0.0095 0.0009 0.0021 0.2518 t-test 0.35 2.39 2.65 2.47 2.48 0.71 CBNP P(T ≤ t) 0.3641 0.0087 0.0043 0.0070 0.0068 0.2386 sampling sites located in three different regions of Northern Vietnam showed significant difference in clustering pattern (fig 4) The sites of each region clustered together and distinctly with other regions Table Global and pair-wise ANOSIM for differences in species and guild compositions of leaflitter spider assemblages between regions Comparison Global CPNP vs TDNP CPNP vs CBNP TDNP vs CBNP (a) Species composition R p 0.742 0.001 0.615 0.001 0.814 0.001 0.811 0.001 (b) Guilds composition R p 0.023 0.143 0.047 0.094 0.017 0.236 - 0.003 0.455 Figure MDS plots of sampling plots in the Northern Vietnam generated by leaf-litter spider species composition sorted according to regions (●) sites in Cuc Phuong National Park; (▽) sites in Tam Dao National Park; (□) in Cat Ba National Park 64 TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 Results of ANOSIM tests (table 3a) also showed significant difference in species composition of canopy spider abundances between CBNP and CPNP (R = 0.814, P < 0.01) as well as between CBNP and TDNP (R = 0.811, P < 0.01), while the difference was decreased between CPNP and TDNP (R = 0.615, P < 0.01) The species composition of leaf-litter spiders of three regions was significantly different and the greatest difference was detected between CBNP and the rest regions The MDS plots generated from relative abundances of different spider guilds in three regions showed no obvious clustering pattern (fig 5) Results of ANOSIM tests (table 3b) also showed no difference in guild composition between regions (P > 0.5) Figure MDS plots of sampling plots in the Northern Vietnam generated by leaf-litter spider guild composition sorted according to regions (●) sites in Cuc Phuong National Park; (▽) sites in Tam Dao National Park; (□) in Cat Ba National Park Meanwhile the SIMPER analysis indicated that the average dissimilarity (Dis-values) in guild composition between regions was very low (Dis of CPNP vs TDNP = 3.60, CPNP vs CBNP = 2.02, TDNP vs CBNP = 3.48) Comparison of species and guild composition among habitats The MDS plots generated from relative abundances of different spider species in habitats showed either the difference in clustering pattern, but also different in significant level in regions as well (fig 6) The difference in clustering pattern in CPNP and TDNP was more significant than CBNP The habitats at each region were grouped into two main clusters, the first cluster is comprised type of habitats have simple-LVS, the second cluster included type of habitats have multi-LVS Results showed that spider species composition was similar between habitats with the same in the vegetation structure and different between two types of vegetation structure Pair-wise ANOSIM tests (table 4a) showed the significant difference in species composition of ground-active spider abundances between habitats of multi-LVS and habitats of simpleLVS (P < 0.01), except pair-wise between DISF vs SHRL of CBNP (P > 0.01) Results also indicated no significant difference among most of habitats the same in the vegetation structure (P > 0.01), except pair-wise between NATF vs DISF of TDNP (P < 0.01) The MDS plot generated from relative abundances of different spider guilds in habitats showed significant difference in clustering pattern (fig 7) Sampling sites in habitats have multi-LVS were clustered together and separated from habitats have simple-LVS 65 Pham Dinh Sac, Tran Thi Anh Thu, Li Shuqiang Pair-wise ANOSIM test also indicated signification differences in guild composition (table 4b) The results showed signification difference in guild composition between Fig MDS plots of sampling plots in the Northern Vietnam generated by leaf-litter spider species composition sorted according to habitats habitats have multi-LVS and habitats have simple-LVS (P < 0.01) while similarity in habitats the same in vegetation structure at TDNP (P > 0.01) Fig MDS plots of sampling plots in the Northern Vietnam generated by leaf-litter spider guild composition sorted according to habitats Close square: natural forest, close circle: disturbed forest, open square: shrub-land, open circle: acacia plantation 66 TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 Table Global and pair-wise ANOSIM for differences in species composition and guild composition of leaf-litter spider assemblages between habitats CPNP TDNP CBNP Comparison R p R p R p (a) Species composition Global 0.694 0.001 0.804 0.001 0.521 0.001 NATF vs DISF 0.344 0.016 0.660 0.008 0.304 0.016 NATF vs SHRL 0.936 0.008 0.884 0.008 0.664 0.008 NATF vs ACAP 0.980 0.008 0.964 0.008 0.740 0.008 DISF vs SHRL 0.736 0.008 0.808 0.008 0.292 0.048 DISF vs ACAP 0.896 0.008 0.852 0.008 0.528 0.024 SHRL vs ACAP 0.192 0.151 0.012 0.437 -0.224 0.090 (b) Guilds composition Global 0.778 0.001 0.711 0.001 0.518 0.001 NATF vs DISF 0.180 0.143 0.440 0.016 -0.160 0.881 NATF vs SHRL 0.008 0.008 0.860 0.008 NATF vs ACAP 0.008 0.988 0.008 0.932 0.008 DISF vs SHRL 0.988 0.008 0.976 0.008 0.792 0.008 DISF vs ACAP 0.008 0.984 0.008 0.844 0.008 SHRL vs ACAP 0.484 0.024 -0.048 0.579 -0.164 0.952 Results of SIMPER analysis indicated that the most dissimilar pair-wise between habitats at each region were between NATF and ACAP of CPNP, between DISF and SHRL of TDNP and between NATF and ACAP of CBNP Two guilds sheet-line weavers and cursorial hunters were the contributor to dissimilarity between these pair-wises (table 5) Table SIMPER analysis of differences in guild composition of leaf-litter spider assemblages between the two most dissimilar habitats of each region Comp (a) CPNP NATF vs ACAP (b) TDNP NATF vs SHRL (b) CBNP NATF vs ACAP Dis 39.62 33.80 25.49 Guild Orb weaver Sheet-line weaver Cursorial hunter Ambush predator Orb weaver Sheet-line weaver Cursorial hunter Ambush predator Orb weaver Sheet-line weaver Cursorial hunter Ambush predator Ab1 16.20 78.20 82.80 11.40 − 110.60 79.80 − − 74.20 69.00 − Ab2 2.40 33.80 43.20 32.40 − 51.80 35.20 − − 46.60 35.60 − ADis 4.66 14.62 13.30 7.05 − 18.11 13.23 − − 10.20 12.24 − Co% 11.76 36.89 33.56 17.79 − 53.56 39.14 − − 40.00 48.02 − (Comp) comparison; (Dis) average dissimilarity; (Ab) average abundance; (ADis) guild-specific contribution to average dissimilarity; (Co%) percentage of average dissimilarity due to guild; (−) not significant DISCUSSION Different habitat structure resulted in different on diversity of leaf-litter spiders had been confirmed by Huhta (1971) [16], Bultman et al (1982) [7], Bultman and Uetz (1982) [5], Olson (1994) [22], Burgess et al (1999) [8], 67 Pham Dinh Sac, Tran Thi Anh Thu, Li Shuqiang Vargas (2000) [36], Liski et al (2003) [19], and Wagner et al (2003) [40] The study results of the leaf-litter spiders in Northern Vietnam showed that abundance, species richness and diversity index were higher in habitats have multi-LVS than habitats have simple-LVS The studies by Huhta (1971), Uetz (1975, 1976 and 1979) [16, 31, 32, 33] indicated diversity of spiders increases with increased litter depth Maybe increase litter depth in habitats have multi-LVS are cause increase in spider community in those habitats As litter depth increases, its vertical layers (in differing stages of decomposition) become more distinct Vertical partitioning of deep litter may be a means by which spider species richness and abundance changes with litter depth [5] Furthermore, changes in litter depth may affect spider community because of increased litter volume [40] Increased volume may lead to increased population sizes and therefore lowered extinction rates Through not difference in characters of vegetation structure, the species composition of leaf-litter spiders was significantly different between regions ANOSIM analysis showed that species composition was significantly different between CBNP and the rest regions CBNP located on an island area that isolated from mainland, the distribution of spider species depends on their aerial dispersal potential and the interaction between patch connectivity and area [3] Over time and with isolation, the number of species on islands created by fragmentation will, if any, decline The common characteristis uniting all island systems is isolation, which can result in properties such as a microcosmic nature and a uniquely evolved biota [13] Possible reasons may be isolation affecting to the share in species composition of spiders between CBNP and others in mainland The CPNP belong to the red river delta tropical monsoon climate condition with stability in factors of weather such as temperatures, humidity gradient maybe were support to assemblages of spiders higher at this region Spider assemblages are highly influenced by ecosystem dynamics such as 68 disturbance, and abiotic factors such as ambient humidity and temperature [4, 3] Temperature, humidity, and other abiotic factors have been shown to influence the abundance and distribution of spiders [43] Russell-Smith (2002) [27] showed spider diversity is related to mean annual rainfall In addition, CBNP affected by maritime climate condition with typhoons and storms that often happened in summer TDNP belong to typifiles the climate of the high mountains with high wins, heavy rain and fog-bank in most of the time Maybe these factors also were relative to the assemblages of spiders in study area Our study showed that the species composition of leaf-litter spiders was significantly different between habitats of multiLVS and habitats of simple-LVS Results of SIMPER analysis of differences in guild composition of ground-active spider assemblages between habitats indicated that both guilds are sheet-line weavers and cursorial hunters together in contributors to dissimilarity between habitats of multi-LVS and habitats of simple-LVS Results also indicated that most of species of sheet-line weavers only found in habitats of multi-LVS, in contrast the species of cursorial hunters were dominant in habitats of simple-LVS Abiotic factors, such as moisture, light, and temperature, may influence spider distribution of the litter spiders [11, 25, 40] Sheet-line weaver spiders such as Amaurobiidae and Linyphiidae may be restricted to the lower litter layers since these smaller spiders have a large ratio of surface area to volume, which could make hygro-thermal regulation more difficult in the upper litter layers [40] In the habitats of multi-LVS, relative humidity is higher compared to the habitats of simple-LVS In this take part in support to the assemblages of sheetline weavers at habitats of multi-LVS Moreover, the complexity of leaf-litter effect to distribution of spiders [16, 31, 32, 5] Taxonomic groupings within the diverse spider community of the forest floor exhibit consistent microhabitat segregation correlated with leaflitter complexity [40] The large sheet-line TẠP CHÍ SINH HỌC, 2012, 34(1): 59-71 weavers were equally distributed across litter depths [40] The funnel web design of sheet-line weaver spiders allows them to live in a retreat that is deeper in the litter layer, thereby protecting them from desiccation [26] The complexity of leaf-litter with the depth higher in habitats have multi-LVS are suitable to the species of sheet-line weavers In contrast, the larger, cursorial hunter spiders may be able to reside in the habitats of open space since they can more readily relocate to shady or moist locations when temperature and moisture levels are unacceptable [17] Therefore, habitats having simple-LVS are suitable to the cursorial hunter spiders Furthermore, ambient light intensity is another abiotic factor that may influence spider distribution in the leaf litter [40] With vegetation cover are higher and thus habitats having multi-LVS were darker than habitats having simple-LVS Decreased light availability in the habitats has multi-LVS in may hinder prey capture by visually oriented cursorial hunter spiders Although some cursorial spiders possible rely on vibratory cues to locate prey, reliance on visual cues for prey detection is important for Lycosidae and Salticidae [18, 11] Sheet-line weaver spiders typically have poorly developed eyes [11] and may be less hindered in capturing prey in the darker As a result, we suggest that the distribution of leaf-litter spiders affected by habitat 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UK ĐA DẠNG NHỆN Ở THẢM LÁ RỤNG RỪNG NHIỆT ĐỚI MIỀN BẮC VIỆT NAM TRONG MỐI LIÊN QUAN TỚI ĐIỀU KIỆN VÙNG VÀ CẤU TRÚC MÔI TRƯỜNG SỐNG Phạm Đình Sắc1, Trần Thị Anh Thư2, Li Shuqiang3 (1) Viện Sinh thái Tài nguyên sinh vật (2) Trường Đại học Cần Thơ (3) Viện Động vật học, Viện Hàn lâm Khoa học Trung Quốc TÓM TẮT Nhện sống tầng rụng tiến hành khảo sát ba vườn quốc gia phía Bắc Việt Nam với điều kiện thời tiết khác bao gồm: vườn quốc gia Cúc Phương (khí hậu nhiệt đới gió mùa đồng sông hồng), vườn quốc gia Tam Đảo (khí hậu nhiệt đới gió mùa vùng núi cao) vườn quốc gia Cát Bà (khí hậu biển) Bốn sinh cảnh chọn để khảo sát vùng bao gồm: rừng tự nhiên rừng bị tác động (có cấu trúc thảm thực vật kiểu đa tầng), bụi rậm rừng keo (có cấu trúc thảm thực vật kiểu đơn tầng) Nhện thu phương pháp rây rụng Tổng số 8.787 cá thể nhện trưởng thành thuộc 251 loài 33 họ thu từ ba khu vực nghiên cứu, bao gồm 2.846 cá thể thuộc142 loài vườn quốc gia Cúc Phương, 3184 cá thể thuộc 137 loài vườn quốc gia Tam Đảo 2.757 cá thể thuộc 124 loài vườn quốc gia Cát Bà Phương pháp thống kê MDS ANOSIM sử dụng để so sánh đa dạng nhện vùng sinh cảnh Thành phần loài nhện khác rõ rệt vùng có khí hậu biển so với vùng khác Các số đa dạng sinh học cao sinh cảnh có cấu trúc thảm thực vật đa tầng Thành phần loài nhện khác rõ rệt hai loại sinh cảnh có cấu trúc thảm thực vật khác Mối liên quan đa dạng nhện đặc điểm cấu trúc loại sinh cảnh thảo luận báo Từ khóa: cấu trúc thảm thực vật, đa dạng, điều kiện vùng, nhện thảm rụng, rừng nhiệt đới, miền Bắc Việt Nam Ngày nhận bài: 2-2-2012 71 ... affecting to the share in species composition of spiders between CBNP and others in mainland The CPNP belong to the red river delta tropical monsoon climate condition with stability in factors of. .. to the habitats of simple-LVS In this take part in support to the assemblages of sheetline weavers at habitats of multi-LVS Moreover, the complexity of leaf-litter effect to distribution of spiders... climate of the high mountains with high wins, heavy rain and fog-bank in most of the time Maybe these factors also were relative to the assemblages of spiders in study area Our study showed that the